The “direct” and “indirect” pathways play crucial roles in movement disorder pathophysiology. Both traverse from the striatum to the internal pallidum and substantia nigra, the latter detouring to external pallidum and subthalamic nucleus. Anatomically, the pathways manifest within the striatofugal bundle that passes radially through the pallidum in the form of pencil-like tracts (first described by Wilson1; figure 1) before leaving the pallidum toward the substantia nigra in the form of a comb described by Edinger in 18962 (figure 2). A century later, these structures can be visualized in the living human brain (figures 1D and 2A).
Footnotes
Teaching slides links.lww.com/WNL/A850
Author contributions
A. Horn: drafting/revising the manuscript, data acquisition, study concept or design, analysis or interpretation of data, accepts responsibility for conduct of research and final approval, acquisition of data, study supervision. Siobhan G. Ewert: drafting/revising the manuscript, data acquisition, accepts responsibility for conduct of research and final approval, acquisition of data. Eduardo Joaquim Lopes Alho: drafting/revising the manuscript, accepts responsibility for conduct of research and final approval, acquisition and analysis of the dark field microscopy footage. M. Axer: data acquisition, accepts responsibility for conduct of research and final approval, acquisition of data, interpretation of measurements. H. Heinsen: drafting/revising the manuscript, data acquisition, analysis or interpretation of data, accepts responsibility for conduct of research and final approval, acquisition of data. Erich Talamoni Fonoff: drafting/revising the manuscript, data acquisition, accepts responsibility for conduct of research and final approval, acquisition of data. J.R. Polimeni: drafting/revising the manuscript, data acquisition, accepts responsibility for conduct of research and final approval, acquisition of data, study supervision, obtaining funding. T.M. Herrington: data acquisition, drafting/revising the manuscript, study concept or design, accepts responsibility for conduct of research and final approval, study supervision.
Study funding
No targeted funding reported.
Disclosure
A. Horn, S. Ewert, E. Alho, M. Axer, H. Heinsen, and E. Fonoff report no disclosures relevant to the manuscript. J. Polimeni reports funding by NIH NIMH R01-MH111438 and NIBIB P41-EB015896 and by the Athinoula A. Martinos Center for Biomedical Imaging. T. Herrington reports funding by NINDS grant K23NS099380 and an American Academy of Neurology/American Brain Foundation Clinical Research Training Fellowship. Go to Neurology.org/N for full disclosures.
References
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